The purpose of this proposal is to replace a 14-year-old Zeiss LSM 210 confocal laser scanning microscope (CLSM) in the Microscopy Services Laboratory (MSL), a core facility in the Department of Pathology and Laboratory Medicine. The past 14 years have seen tremendous growth in the use of this confocal microscope in numerous areas of research. Last year, the LSM 210 was used by 109 scientists working under 51 principal investigators from 25 departments. This instrument is used extensively, but it is hopelessly out of date and is not upgradeable. It is no longer supported by Zeiss (even for spare parts), it uses ancient computer technology, and it is at risk of catastrophic failure. A new CLSM in this core facility will greatly expand research capabilities of investigators. Researchers now use multiple fluorescent labels; many studies require subcellular imaging deep within an aqueous mounted sample; several hundred images may be required for a single data collection run. The use of acustico optical tunable filters (AOTF) to control excitation beam intensity, a variable )inhole for each of the three super sensitive photo-multiplier tube (PMT) detectors for control of emission intensity and confocal resolution, extremely flexible beam scanning control allowing user defined regions of interest, a rich selection of laser excitation lines, and superior computer technology combine in the new CLSM to produce an instrument that will serve researchers at UNC well into the future. Members of the MSL staff are experts in microscope imaging technology and are skilled in functioning as a service facility. They will be guided by an internal advisory committee. The MSL is well supported by the School of Medicine and occupies 2000 sq. ft. of space centrally located in the medical complex. A new CLSM in this facility will benefit the medical research community at UNC by making this new technology most accessible to investigators. This is a re-application that is almost completely revised. Because two new Multi-Photon CLSMs are being purchased on our campus, we have removed the multi-photon portion of our request and we have modified the major user group. Substantial preliminary and published data have been added to project descriptions.